1. Field of the Invention
The present invention relates to a probe washing unit and an automatic analysis system, particularly of a random access type, provided with the probe washing unit.
2. Discussion of the Background
In a usual random access type automatic analysis system, when a sample in a sample container such as sample tube accommodated in a sampler, for example, is sucked and discharged into a reaction tube by utilizing a slender dispensation, i.e. sample probe, the sample usually in a liquid state adheres to the outer surface of the tip end of the probe at the time of suction and may be dropped into the reaction tube together with the sample inside the probe to be weighed at the time of discharge, thus deteriorating the sample dispensing precision as well as the measurement precision.
In order to obviate such defects, the sample adhering to the outer surface of the tip portion of the probe is removed by wiping the same or dipping the same into a clean liquid such as pure water.
In the wiping method, the tip portion of the probe is held by a wiper having a liquid absorbing property and moving the probe upward. On the other hand, in the dipping method, the dispensation probe is dropped in a washing unit during the analyzing process after sucking the sample and the sample adhering to the outer surface of the probe tip is diffused by washing water in the washing unit and then wiped.
Furthermore, when dispensing a sample and a reagent in the automatic analysis system, the inside and outside of the dispensation probe are washed in the washing unit after the sample and the reagent are dispensed. However, since a drop of the washing water is typically attached to the probe after the washing, the drop is wiped off and likely removed as in the case of the above mentioned wiping method.
However, in the wiping method, since various samples are treated by the wiper one after another, these become stained and cause contamination of the samples. In particular, the recent type of an automatic analysis system operates with a high degree of sensitivity, and hence, that with the normal value being several tens, for example, in AFP (Anti-Feto-Protain) the measurement becoming several thousands according to the condition of a patient, if the sample is sucked from the patient, thus bringing about a problem of a minute contamination of the samples.
On the other hand, in the dipping method, even if a high-speed operation of the automatic analysis system is realized, too much time is required for the vertical motion of the dispensation probe in the washing unit during the horizontal transfer of the dispensation probe, and, hence, there still remains a disadvantage of not coping with the high-speed operation. Now, therefore, in order to cope with the high-speed operation, a proposal has been made such that the dispensation probe the washed with flushing water with its tip, i.e. front, portion kept at a transfer height at a flushing position. However, in this method, since the flushing water is applied to the dispensation probe for washing the same, the probe will be transferred to the next vessel position with a drop of water being attached to the probe tip after the stopping of the water feed. As a result, the drop of water having attached to the probe tip is scattered or the drop is mixed into the sample or reagent, thus causing a disadvantage such as providing inferior data precision or degraded and denatured reagent and sample.